chore(proto): remove default value from NEM payload

[no changelog]

common/protob/messages-nem.proto

@@ -58,7 +58,7 @@ message NEMSignTx {
     message NEMTransfer {
         required string recipient = 1;              // Address of the recipient
         required uint64 amount = 2;                 // Amount of micro NEM that is transferred
-        optional bytes payload = 3 [default=""];    // Actual message data (unencrypted)
+        optional bytes payload = 3;                 // Actual message data (unencrypted)
         optional bytes public_key = 4;              // Public key of the recipient (for encrypted payloads)
         repeated NEMMosaic mosaics = 5;             // Attached mosaics
         /**

core/src/apps/nem/transfer/serialize.py

@@ -93,7 +93,7 @@ def get_transfer_payload(
         encrypted_payload = _encrypt(node, transfer.public_key, transfer.payload)
         return encrypted_payload, True
     else:
-        return transfer.payload, False
+        return transfer.payload or b"", False
 
 
 def _encrypt(node: bip32.HDNode, public_key: bytes, payload: bytes) -> bytes:

core/src/trezor/messages.py

@@ -4722,7 +4722,7 @@ if TYPE_CHECKING:
     class NEMTransfer(protobuf.MessageType):
         recipient: "str"
         amount: "int"
-        payload: "bytes"
+        payload: "bytes | None"
         public_key: "bytes | None"
         mosaics: "list[NEMMosaic]"
 

python/src/trezorlib/messages.py

@@ -6064,7 +6064,7 @@ class NEMTransfer(protobuf.MessageType):
     FIELDS = {
         1: protobuf.Field("recipient", "string", repeated=False, required=True),
         2: protobuf.Field("amount", "uint64", repeated=False, required=True),
-        3: protobuf.Field("payload", "bytes", repeated=False, required=False, default=b''),
+        3: protobuf.Field("payload", "bytes", repeated=False, required=False, default=None),
         4: protobuf.Field("public_key", "bytes", repeated=False, required=False, default=None),
         5: protobuf.Field("mosaics", "NEMMosaic", repeated=True, required=False, default=None),
     }
@@ -6075,7 +6075,7 @@ class NEMTransfer(protobuf.MessageType):
         recipient: "str",
         amount: "int",
         mosaics: Optional[Sequence["NEMMosaic"]] = None,
-        payload: Optional["bytes"] = b'',
+        payload: Optional["bytes"] = None,
         public_key: Optional["bytes"] = None,
     ) -> None:
         self.mosaics: Sequence["NEMMosaic"] = mosaics if mosaics is not None else []